Volume 34, Issue 5-6

The present review covers almost 100 polymeric MFe (M=Li, Na, K, Rb, and Cs) compounds. The metal atoms of group 1 as partners with iron atom build up complex polymeric chains. The iron atoms are found in the oxidation states 0, +2, and +3, of which the oxidation state +3 prevails. The coordination number of the iron atom ranges from 2 to 10 (sandwiched). The coordination sphere about the main group 1 metals varies, ranging from tetrahedral to mostly trigonal bipyramid. There are also higher coordination numbers involved, namely, from 6 to 10. The most common ligand atoms are oxygen and nitrogen. There are three compounds displaying distortion isomerism. Several relationships between structural parameters are found and discussed.

The title compounds [R 2 NH 2 ][C 2 O 4 SnMe 3 ](R= i -Bu, Cy), in which tin atoms adopt a distorted trigonal bipyramidal configuration, have been prepared and submitted to an X-ray diffraction study. These compounds have been obtained from the reaction of (Cy 2 NH 2 ) 2 C 2 O 4 ·H 2 O or ( i -Bu 2 NH 2 ) 2 C 2 O 4 with SnMe 3 Cl. In both [R 2 NH 2 ][C 2 O 4 SnMe 3 ] compounds, the trans complex has an almost regular trigonal bipyramidal geometry around the tin atom. The SnMe 3 residues are connected as a chain with bridging oxalate anions in a trans -SnC 3 O 2 framework, the oxygen atoms being in axial positions. The cations connect linear adjacent chains through NH…O hydrogen bonds giving layered structures.

A series of organotin(IV) derivatives of bis(pyrimidin-2-ylthio)methane ( ptm ), 1,2-bis(pyrimidin-2-ylthio)ethane ( pte ) and 1,6-bis(pyrimidin-2-ylthio)hexane ( pth ) have been prepared in dichloromethane at room temperature. The 2:1 (M/L) molar ratio compounds have a general formula of [Sn 2 Cl x Ph 8- x L] ( x =2, 4, 6, 8; L= ptm , pte and pth ). A 1:1 complex was also obtained by reacting SnClPh 3 with pth . The organotin derivatives were characterised by multinuclear NMR ( 1 H, 13 C and 119 Sn) and infrared spectroscopy, gel permeation chromatography (GPC), microanalysis and melting point. In the triphenyltin derivatives, 1 , 5 , 9 and 10 the tin atoms show a distorted trigonal-bipyramidal configuration where the ligand is monodentate towards the metal atom. In the compounds 2 – 4 , 6 – 8 and 11 – 13 , the tin atoms each exhibit a distorted octahedral configuration. Chelation is formed between the tin nucleus and the coordinating sulphur and nitrogen atoms. The correlation between the 1 J ( 13 C- 119 Sn) and C-Sn-C bond angle indicates formation of 5-coordinate compounds.

The new ligands 3-(2-methyl-2,3-dihydro-benzthiazo-2-yl)-chromen-2one (AcBzH) and N′-[1-2-oxo-2H-chrome-3yl-ethylidene]-hydrazinecarbodithionic acid benzyl ester (AcBDTZH) were prepared by the reaction of 3-acetyl- 2H -chromen-2-one with 2-aminothiophenol and S-benzyl dithiocarbazate, respectively. The germanium(IV) complexes have been prepared by reacting Ph 3 GeCl and Me 3 GeCl in 1:1 molar ratio with these monofunctional bidentate AcBzH and AcBDTZH ligands by using microwave as well as conventional heating methods for comparison purposes. All the synthesized compounds were characterized by elemental analyses, melting point, IR, 1 H-NMR 13 C-NMR, mass and X-ray powder diffraction techniques. These studies showed that the ligands coordinated to the germanium atom in a monobasic bidentate manner and trigonal bipyramidal environment around the germanium atom have been established for the complexes. To evaluate the effect of metal ion upon chelation, both ligands and their complexes have been screened for their antimicrobial activity against the various pathogenic bacterial and fungal strains. The metal complexes have shown antimicrobial activity as compared to the free ligands. The pesticidal activity and DNA cleavage activity of both ligands and their metal complexes have been tested and discussed.

Biologically potent complexes of aluminum(III) and gallium(III) derived from semicarbazone of 3-acetylcoumarin have been synthesized under microwave irradiation and investigated using a combination of microanalytical analysis, melting point, ultraviolet spectra, infrared spectra, 1 H nuclear magnetic resonance (NMR) spectra, and 13 C NMR spectra. Aluminum and gallium isopropoxides interact with the ligand, resulting in the formation of colored products. Based on conductance and spectral evidences, a five-coordinated structure for aluminum(III) and gallium(III) complexes has been assigned for 1:1 ratio and a six-coordinated structure for 1:2 and 1:3 ratios. The ligand is coordinated to the aluminum(III) and gallium(III) via the azomethine nitrogen atom and the enolic oxygen atom. The free ligand and its metal complexes have been tested in vitro against a number of pathogenic microorganisms in order to assess their antimicrobial and pesticidal properties. Both the ligand and its complexes were found to possess appreciable bactericidal and pesticidal properties.

Solid-state and solution 117 Sn nuclear magnetic resonance studies of C 2 O 4 (SnPh 3 ) 2 have been carried out and found to be in good agreement with the tetrahedral environment of the tin (IV) atom as found from the solid state structure, previously determined by a single crystal X-ray diffraction analysis.